It is probable that the Subcarboniferous series north and west of

the region last described, has been affected by a similar movement. Facts that are coming to light in Knox, Coshocton, Holmes and other counties seem to point in this direction.

In Washington county several lines of moderate uplift have long been known. Special interest has centered in them as sources of petroleum. They are described in the chapter on the Macksburg Oil Field.

The difficulty of determining the dip in the shale series of northeastern Ohio has already been pointed out. It arises from the absence of easily recognized horizons in this formation. In the deep ravines and gorges by which the shales are traversed, opportunities are occasionally afforded to follow particular beds for a mile or two, and thus to note their flexures, but it is only when the Berea grit above the shales is reached, or when the drill strikes the Devonian limestone underneath them, that we acquire horizons clear and trustworthy enough to be used in large and connected calculations of the dip in which all the strata share. The Berea grit has been used as largely as possible for this service, and a considerable number of facts pertaining to the structure of the regions in which it is found are given in Chapter IV. In its outcrops in Lorain, Erie and Huron counties particularly, the local disturbances involving this formation are numerous and considerable. There are but few of the sandstone quarries in which steep dips are not found, the directions of which sometimes change in a single quarry. Adjacent quarries show the opposite sides of anticlinals in some instances. The facts have sometimes been explained as resulting from glacial agencies, but in all the sections in which the shales underlying the Berea grit are exposed to view, they are found to share fully in the flexures of the sandstone cover. It may well be that the sharply inclined portions of the Berea grit were best protected against denudation and glacial erosion, and that the frequency of quarries with steep slopes results from this fact. The larger undisturbed or less disturbed portions of the once universal formation have been swept away by the agencies of waste.

There is, however, a ridge of high-lying Berea sandstone that runs parallel to the shore of Lake Erie, though distant from it thirty or more miles, that demands a different explanation. All the sections involving the continuity of the Berea grit southward from the lake shore, display a low arch at this point, and when the elevations of the Berea grit are tabulated a line becomes apparent. At Mecca, the Berea grit is about 925 feet above tide at Akron, it is nearly the same elevation, viz., 910 to 930 feet; at Shelby, it is 945 feet, and at Plymouth about 990 feet. This line of facts has been noticed before, viz., in Vol. I, Geology of Ohio,

page 40, but the explanation there offered of the facts, viz., that the apparent uplift is due to the great thickening of the shale series to the southward, fails to cover the ground. The shale series expands from 800 feet at Elyria to 1,860 feet at Akron, as is elsewhere shown, but where the sandstone lies highest, at Shelby and Plymouth, the shales are but 650 feet thick, which is 150 or more feet less than at Elyria. The Berea grit at Plymouth is 300 feet higher than the same stratum at Elyria. The only explanation of the facts that appears adequate, is the obvious one that a low anticlinal extends from Shelby through Akron to Mecca, in a line about N. 70° E.

It is this Akron arch that constitutes the watershed of northern Ohio for at least a part of its extent. It also seems to provide a natural southern boundary for Lake Erie. The lake basin would, according to this view, be a synclinal.

It must be acknowledged, however, that we have not yet facts enough to fully establish the continuity of the fold that is here suggested. The points from which measurements are reported are so far apart that there is room between them for depressions in the stratum on which we rely. In accordance with such a view, Akron might lie on one low axis and Shelby on another.

The first explanation suggested is believed to be most consonant with all the facts in hand.

To sum up the statements now made, we know but comparatively few arches in Ohio, and these few are moderate in slope and small in height. Fuller knowledge of our geology will doubtless give us a larger number of these low folds, but there is little probability that any sharp and well defined anticlinals have altogether escaped notice. Those that remain to be discovered will agree with those already known, in breaking up the monotony of our series by the suspension or occasional reversal of the prevailing dip and in requiring close and accurate measurements for their detection.

By untrained observers, the watersheds of our drainage channels are often mistaken for anticlinals. If anticlinals traverse the series where these identifications are made, they may well serve to divide the drainage systems from each other, but such "divides" do not by any means require these structural accidents as the conditions on which they depend. Anticlinals must be demonstrated, not inferred.

The problems of our geology in this field are dependent on the use of the level. Accurate and connected series of elevations of well-settled horizons are indispensable to their solution. In the First Geological Survey of the state, Whittlesey recognized the need of physical determinations of the various elements of our coal fields in particular, and he began at that time a valuable series of measurements, but his work was of necessity hampered by a want of well-determined geological horizons. The essential facts of identification of strata, without which the most careful measurements are futile, could only be secured by the prolonged study and the economical development of the field, the latter by means of the introduction of railway lines and the utilization of its minerals on a large scale.

This work of development has now been carried forward on both the scientific and the economic sides to such a point that definite solutions of many of the questions of our structural geology are easily attainable.

There are but few districts known in Ohio in which disturbances are to be found that fairly deserve the name of faults. In the northeast corner of Adams county and in adjacent territory, there are a number of square miles throughout which the strata are really dislocated. The Berea grit is found in contact with the Niagara shale in some instances. The throw of such faults must be at least 400 feet. Faults of this character in Ohio geology are as unusual and unexpected as trap dykes in northern Kentucky, the latter of which have been recently reported by Crandall (Ky. Geol. Survey).

In Geology of Ohio, Vol. V, page 262, mention was made of a small area of disturbance in the vicinity of Mineral Point, Tuscarawas county. No new facts have been gathered from this region. The Findlay monoclinal has been referred to already, and will be further described in a subsequent chapter.

The account of our structural geology, here given, seems called for in this connection by reason of the prominence that is given to anticlinals in the discussion and discovery of the recent natural gas supply of western Pennsylvania. The great wells upon which Pittsburgh depends are unquestionably located on the summits of pronounced folds. This fact has led to an eager inquiry in regard to similar folds in Ohio. The answer to such inquiries is that folds similar and equal to the great anticlinals of western Pennsylvania and West Virginia were never formed and consequently will never be found in Ohio. Our supply of this much-prized and eagerly-sought fuel, whatever it shall prove to be, must be independent of any conspicuous and easily-traced folds in our surface rocks.

CHAPTER II.

THE ORIGIN AND ACCUMULATION OF PETROLEUM AND NATURAL GAS.

BY EDWARD ORTON.

Natural gas and petroleum belong in a list of products of the crust of the earth to which we give the name of bitumens. Other bodies in the same list are the semi-fluid maltha and the solid asphaltum. All of these substances unquestionably have a similar, general history. They are found under the same conditions and the transitions from one to another, as of petroleum to asphalt, can be often noted. They are technically known as hydrocarbons, carbon and hydrogen constituting almost their entire substance, the former making about 85 per cent. and the latter about 13 per cent. of them.

They have long been known to man, and their use antedates history, but the importance which they now possess in the civilized world is of quite recent date. The discovery and use of petroleum on the large scale is included within the last twenty-five years, and all of the really important applications of natural gas belong to our own day, and are now in their initial stages.

Within the last fifty years, and particularly within the last twentyfive years, much has been written by geologists and chemists upon the origin and modes of accumulation of petroleum and gas.

Our knowledge as to the conditions of their occurrence in the rocks has been very greatly extended, and various theories have been advanced to account for the facts brought to light. There is no one theory that commands universal acceptance, and here, as elsewhere, it is no doubt true that theories are sometimes found opposed to each other because they respectively regard but one side of a subject which has more than one side.

Brief statements of the more commonly received views as to the origin and accumulation of these bituminous compounds will here be given. The statements are mainly derived from the excellent work of Prof. S. F. Peckham, on "Petroleum and its Products, " contained in the 10th volume of the special reports of the United States Census Bureau

for 1880, to which the reader who desires fuller discussions of the subjects here treated must refer.

A. ORIGIN.

The theories as to the origin of petroleum and natural gas can be divided into two main groups, viz., (1) those which refer these bodies to inorganic sources, or in other words, which make them the result of chemical affinity acting on mineral matter, and (2) the theories that regard them as the result of a partial decomposition of vegetable or animal substances that have been stored up in the rocks.

These two classes of theories will be briefly considered.

I. THEORIES OF CHEMICAL ORIGIN.

It has been claimed by a number of chemists, some of whom have high standing in the scientific world, that the several members of the series now under consideration can be referred to a purely mineral origin.

1. In 1866, the distinguished French chemist, Berthelot, propounded a theory that would, in his view, account for all of the natural hydrocarbons in this way. He supposed the alkali metals, viz., potassium and sodium, to exist in the interior of the earth in a free or uncombined state and, necessarily, at a high temperature. If, now, water carrying in solution carbonic acid-and the crust of the earth abounds in both should find access to these metals, he pointed out the steps of the chemical action that must take place, and that would result in the formation of a series of hydrocarbon compounds. In this case, the process of oil and gas formation would be deep-seated and continuous, the reactions that give birth to them being constantly renewed in the recesses of the earth.

2. Another theory that invokes chemical force only for the origin of these bodies, was advanced by the eminent Russian chemist, Mendeljeff, in 1877. It attracted a large measure of attention and interest throughout the scientific world. He supposed the interior of the earth to contain large masses of metallic iron, and also metallic carbides (compounds of carbon and metals), all at a high temperature. The contact of water under these conditions with these bodies would, in his

view, generate metallic oxides and hydrocarbons. Mendeljeff, accordingly, holds that petroleum is never of organic origin, but is as purely & product of chemical affinity as a veinstone, or an ore. It would follow from this theory, also, that the process of oil and gas formation is con